1. Field of the Invention
This invention relates to rotary engine structures and in particular to means for cooling the rotors of such engines.
2. Description of the Prior Art
In U.S. Pat. No. 3,206,108 of Hubert Abermuth, a rotary piston internal combustion engine is disclosed wherein the piston is provided with passages and cavities adapted to convey lubricant serving as a liquid cooling medium. The coolant carrying passages include radial passages in the piston substantially in the axially located central transverse plane of the piston and axial passages in the piston at opposite sides of the sealing strip. The axial passages are closed at their opposite ends and the radial passages communicate with the axial passages adjacent the center thereof. The piston further includes radial passages extending from the opposite ends of the axial passages inwardly toward the axis of the piston to an annular chamber within the piston. The Abermuth structure requires the provision of a web in the center of the rotor which not only increases the mass of the rotor but makes the rotor substantially more expensive in requiring complicated manufacturing processes such as including complicated coring.
Other prior art of some pertinency to the problem of rotor cooling includes the British patent specification No. 893,938 of NSU Mohorenwerke Aktiengesellschaft and Wankel GmbH. In said British patent, the rotor is provided with an internal cavity with inlet and outlet openings for the flow of a cooling liquid therethrough. A partial flow of the liquid is branched off for lubrication of the bearing surfaces.
In British patent specification No. 928,419, of Daimler-Benz Aktiengesellschaft, a means for cooling the piston of a rotary piston engine is disclosed wherein a liquid coolant is supplied through a hollow engine shaft and forced through an annular passage in the piston which is divided into two halves by a partition extending at right angles to the shaft axis. Coolant admission bores are provided opening into one-half of the annular passage near the middle of each of the piston sides and return bores are provided leading away from the other half near the middle of each of the piston sides. The coolant may be lubricating oil which is also used to lubricate the engine.
In U.S. Pat. No. 3,269,370 of Hanns-Dieter Paschke et al, a rotor cooling means for a rotary mechanism is disclosed wherein cooling fluid is collected by a collecting member attached to the eccentric shaft of the engine for rotation therewith relative to the rotor. A plurality of cooling compartments of the rotor periodically move into communication with cooling collecting pockets of the cooling collecting member. One collecting pocket has an opening which periodically communicates with rotor openings communicating with compartments in the rotor interior as the rotor rotates relative to the eccentric end shaft. The cooling fluid is periodically directed radially inwardly where it is collected in the collecting pockets and discharged from the engine.
Yasuo Tatsutomi, in U.S. Pat. No. 3,302,624, shows a rotary piston and cooling means therefor which cools the rotor by circulation of cooling fluid as a result of the action of alternate acceleration and deceleration of the rotational velocity of the piston. The piston includes vanes extending radially outwardly within a hollow interior thereof and at an angle to a radial plane through the axis of rotation. The lateral end walls are provided with apertures between the vanes for passing the cooling fluid.
Wolf-Dieter Bensinger et al U.S. Pat. No. 3,444,842 shows a rotary piston internal combustion engine wherein an annular space is provided within the hub which is subdivided by walls arranged to centrifuge the lubricating oil. A collecting screen is provided within an area of the end wall of the eccentric for conducting the collected oil in an axial direction. The patentees point out that in case of need, the oil conducted through the piston may also be utilized to cool the piston.
Wolf-Dieter Bensinger, in his U.S. Pat. No. 3,469,505, shows another means for cooling a rotary piston wherein only the corners of the piston are cooled by oil escaping out of the bearing of the piston and bearings of the eccentric shaft. The piston corners may be provided with apertures along the radially outer circumference of an annular groove parallel to the end wall of the piston and covered by ribs.